http://spssx-discussion.165.s1.nabble.com/Question-About-Tests-of-Normality-and-Choice-of-Statistical-Analysis-tp5728302p5728315.html
Bruce,
That is very nice.
But you never even mentioned the assumptions of the relevant non-parametric
tests that are based on the rank-transformation: continuous data of similar-
shape distributions in both samples, and few ties. Some of your examples
("Normal versus skewed") would not be appropriate for testing by ranks.
Likert-type items deserve normal testing for various reasons, including the
occasional weird scoring that you can observe as resulting from rank-transforms.
Continuous items with similar skew, etc., usually should be transformed by taking
logs or reciprocal (whatever is appropriate) to "normalize"
- That improves both the metric and the test. I can regard rank-testing as a sloppy,
time-saving expedient, compared to doing a transformation that is apparent.
- If there is not a transformation available, then there is big doubt about whether
these data fit the non-par assumption.
--
Rich Ulrich
> Date: Wed, 31 Dec 2014 09:39:59 -0700
> From:
[hidden email]> Subject: Re: Question About Tests of Normality and Choice of Statistical Analysis
> To:
[hidden email]>
> Hi Brian. My thoughts on testing for normality as a precursor to a
> parametric test are summarized in a conference presentation I gave a few
> years ago. A PDF of the slides can be found here:
>
>
https://www.nosm.ca/uploadedFiles/Research/Northern_Health_Research_Conference/Weaver,%20Bruce_Silly%20or%20Pointless%20Things.pdf
>
> Cheers & Happy New Year.
> Bruce
=====================
To manage your subscription to SPSSX-L, send a message to
(not to SPSSX-L), with no body text except the
command. To leave the list, send the command
SIGNOFF SPSSX-L
For a list of commands to manage subscriptions, send the command
INFO REFCARD